Toward Epoch of Reionization Measurements with Wide-Field Radio Observations

By Miguel F. Morales, Jacqueline N. Hewitt. 2003

198 citations recorded by the source corpus.

This paper explores the potential for statistical epoch of reionization (EOR) measurements using wide-field radio observations. New developments in low-frequency radio instrumentation and signal processing allow very sensitive EOR measurements, and the analysis techniques enabled by these advances offer natural ways of separating the EOR signal from the residual foreground emission. This paper introduces the enabling technologies and proposes an analysis technique designed to make optimal use of the capabilities of next-generation low-frequency radio arrays. The observations we propose can directly observe the power spectrum of the EOR using relatively short observations and are significantly more sensitive than other techniques that have been discussed in the literature. For example, in the absence of foreground contamination the measurements we propose would produce five 3 σ power spectrum points in 100 hr of observation with only 4 MHz bandwidth with LOFAR for simple models of the high-redshift 21 cm emission. The challenge of residual foreground removal may be addressed by the symmetries in the three-dimensional (two spatial frequencies and radio frequency) radio interferometric data. These symmetries naturally separate the EOR signal from most classes of residual unsubtracted foreground contamination, including all foreground continuum sources and radio line emission from the Milky Way.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a94986ed148464f6dbe9a0e798d77fd3d98b10b2

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Citations in the corpus

Reionization and the Cosmic Dawn with the Square Kilometre Array (2012, background): “We note that this is very similar to what was found in Morales & Hewitt (2004) but provides a somewhat more intuitive picture.”
Studying reionization with Lyα emitters (2007, methodology): “…these difficulties, the Mileura Widefield Array and the Low Frequency Array will start dedicated observations of this emission in the coming years (Morales & Hewitt 2004; de Vos 2004), and the 21cm Array and the Giant Meter-wave Radio Telescope are already being used to perform these measurements…”
21 cm Tomography with Foregrounds (2005, methodology): “Although 21 cm foregrounds have been discussed in some previous papers (e.g., DiMatteo et al. 2002, 2004; Morales & Hewitt 2004; Oh & Mack 2003; Santos et al. 2005; Zaldarriaga et al. 2004), the questions on how to remove foregrounds and noise from observations of the 21 cm signal, how well it can…”
IMAGING THE EPOCH OF REIONIZATION: LIMITATIONS FROM FOREGROUND CONFUSION AND IMAGING ALGORITHMS (2011, background): “…kx, ky, and kz are comoving wavenumbers along three spatial axes with origin at some point about which the EoR fluctuations will be estimated, then Morales & Hewitt (2004) have shown that k⊥ = √ k2x + k 2 y , kx = 2πu DM (z) , ky = 2πv DM (z) , kz = k|| ≈ η 2πHofHIE(z) c(1 + z)2 , (12) where the…”
FIRST SEASON MWA EOR POWER SPECTRUM RESULTS AT REDSHIFT 7 (2016, methodology): “The noise is mostly constant across k|| because the thermal noise amplitude is relatively constant over frequency and the Fourier transform distributes the noise power across all modes (Morales & Hewitt 2004).”
Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR (2020, background): “We also define the wavenumber k = (kl, km, k‖) as (Morales & Hewitt 2004; McQuinn et al. 2006) : kl = 2πu DM (z) , km = 2πv DM (z) , k‖ = 2πH0ν21E(z) c(1 + z)2 η, (24) where H0 is the Hubble constant, ν21 is the frequency of the hyperfine transition, and E(z) is the dimensionless Hubble parameter…”
A PER-BASELINE, DELAY-SPECTRUM TECHNIQUE FOR ACCESSING THE 21 cm COSMIC REIONIZATION SIGNATURE (2012, methodology): “…can be achieved between foregrounds and higher spatial Fourier-domain k-modes of the spherically averaged 21cm reionization power spectrum ∆221(k), as foreground removal techniques generally rely on the spectral smoothness of foreground emission to isolate the 21cm signal (Morales & Hewitt 2004).”
Calibration requirements for detecting the 21 cm epoch of reionization power spectrum and implications for the SKA (2016, methodology): “Statistical measurements of the EoR show the most promise for a robust detection in wavenumber space (Morales & Hewitt 2004), represented by {kx, ky, kz} and accessible through Fourier transforms.”
THE IMPACT OF POINT-SOURCE SUBTRACTION RESIDUALS ON 21 cm EPOCH OF REIONIZATION ESTIMATION (2012, methodology): “…visibilities forms the maximum likelihood estimate. where the Fourier modes are in units of inverse distance (Mpc−1), and are given by (Peebles 1993; Morales & Hewitt 2004, and references therein): k⊥ = 2π |u| DM (z) , (7) k‖ = 2πH0f21E(z) c(1 + z)2 η, (8) where DM (z),H0, f21, z are the…”
Science with the Murchison Widefield Array (2012, background): “The signal-to-noise ratio (S/N) in each pixel will be .”
A model of diffuse Galactic radio emission from 10 MHz to 100 GHz (2008, methodology): “In due time, NHT experiments such as LOFAR (Rottgering 2003; Rottgering et al. 2003; Zaroubi & Silk 2005), MWA (Morales & Hewitt 2004; Morales 2005; Bowman et al. 2006) and 21 CMA (Peterson, Pen & Wu 2006) will produce accurate low-frequency maps of Galactic emission much like CMB experiments have a”
21-cm fluctuations from inhomogeneous X-ray heating before reionization (2006, methodology): “In the analysis that follows, we assume that foreground removal can be affected by exploiting the smoothness of foregrounds in frequency space (Morales & Hewitt 2004; Zaldarriaga et al. 2004; Morales 2005; Santos et al. 2005; McQuinn et al. 2006; Wang & Hu 2006).”
Reionization and Cosmology with 21-cm Fluctuations (2009, background): “The key to foreground subtraction is the spectral smoothness of the synchrotron and free-free emission (Di Matteo, Ciardi & Miniati 2004, McQuinn et al. 2007, Gnedin & Shaver 2004, Santos, Cooray & Knox 2005, Zaldarriaga, Furlanetto & Hernquist 2004, Morales & Hewitt 2004).”
INTENSITY MAPPING WITH CARBON MONOXIDE EMISSION LINES AND THE REDSHIFTED 21 cm LINE (2011, background): “…for the redshifted 21 cm signal: one can distinguish foregrounds from the underlying signal by using the fact that the foregrounds are spectrally smooth, while the signal has structure in frequency space (e.g. Zaldarriaga et al. 2004, Morales & Hewitt 2004, McQuinn et al. 2006, Petrovic & Oh 2010).”
Upper Limits on the 21 cm Epoch of Reionization Power Spectrum from One Night with LOFAR (2017, methodology): “2) should only change very slowly with frequency and thus separable from the spectrally fluctuating 21- cm EoR signal (e.g. Morales & Hewitt 2004).”
Simulating cosmic reionization at large scales – II. The 21-cm emission features and statistical signals (2006, background): “The differential brightness temperature with respect to the CMB of the redshifted 21-cm emission is determined by the density of neutral hydrogen,ρHI, and its spin temperature,Ts (see e.g. Morales & Hewitt 2004; Shapiro et al. 2005, for detailed discussions).”